Power divider circuit



y 9 1952 w. w. SALISBURY 2,605,357

POWER DIVIDER CIRCUIT Filed Sept. 14, 1945 Patented July 29, 1952 POWER DIVIDER CIRCUIT Winfield W Salisbury, Cedar Rapids, Iowa, as-

signor, by mesne assignments, to the United States of America as representedby the Secretary of the Navy Application September 14, 1945, Serial No. 616,415

8 Claims.

This invention relates to a radio frequency power divider circuit, and particularly to one where the power may be divided in any suitable proportion between two outputs without materially changing the combined impedances of these outputs as seen from the input.

It is therefore an object of this invention to provide a means for dividing in any suitable proportion the radio frequency power output to a pair of transmission lines.

It is another object of this invention to provide a means for dividing in any suitable proportion the radio frequency power output to a pair of transmission lines and having incorporated therewith a means for regulating said proportion at will.

It is another object of this invention to provide a transmission line construction having an input line, and a pair of output lines joined thereto with a means for dividing in any suitable proportion the power output from each of said parallel output lines without materially disturbing the effective terminating impedance of said input lines.

Other objects and features of the present invention will become apparent upon a careful consideration of the following detailed description when taken together with the accompanying drawing, wherein:

Fig. 1 is a sectional elevational view of an embodiment of the invention.

Fig. 2 is a cross-sectional view taken along the line II-II of Fig. 1.

Fig. 3 is a generally sectional elevational view of a second embodiment of the invention.

Fig. 4 is a sectional view taken along the line IVIV of Fig. 3. 7

An embodiment of the present invention is shown in Fig. 1, the input transmission line is at I and the output transmission lines are shown at IOI and I02. The outer conductors of the three transmission lines connect together at a common junction, the power dividing arrangement being provided in the circuits of the inner conductor.

The end portion I03 of the inner conductor of the transmission line I00 is mounted for axial rotation in the ball bearings I04 and is separated from the remainder of the inner conductor I00a of the transmission line I00 by a rotating joint of the contactless type formed by the hollowing out of the left-hand end of the conductor I03 and the projection of an extension I002) of the conductor I00a into the hollowed out portion of the conductor I03 for an electrical length of approxi- 2 mately 3, quarter-wave length, in accordance with the principles described in my patent application, Serial No. 478,793, filed March 11, 1943, now U. S. Patent Serial No. 2,541,836 of February 13, 1951.

The outer conductor of the transmission line I00 is enlarged slightly in the neighborhood of the junction. In the space thus provided are mounted two semi-cylindrical conducting segments I06 and I01 having axial lengths of approximately a quarter-wave length and oriented coaxially with the conductor I03. The segment I06 is electrically and mechanically connected to the inner conductor of line MI and the segment I0! is electrically and mechanically connected to the inner conductor of line I02 and the respective connections are made at one end of the respective segments. Within the segments I06 and I0! are two more segments coaxial therewith and also of an axial length approximately a quarter-wave length, these segments begin to show at I08 and I09. The segment I08 is preferably approximately semi-cylindrical, although it may, if desired, be smaller in circumference, that is, it may be only a quarter cylinder or the like. preferably by soldering, on suitable flanges of the conductor I03, such flanges being shown at H!) and II I. The segment I09 is mounted on the flange III but its left-hand axial extremity is free and makes no contact with either the flange H0 or with the neighboring portion of the conductor I03. The segment I09 has the function of a shield to reduce coupling between the lefthand portion of the conductor I03 and one of the outer segments when the segment I08 is located wholly opposite the other of the outer segments.

The right-hand portion of the conductor I03 carries a choke member II3 which is adapted to.

provide a radio-frequency short circuit between the conductor I03 and the immediately adjacent portion of the outer conducting structure of the junction, in accordance with the principles described in my above-mentioned patent application. The choke member I I3 defines an annular cup having an electrical length of approximately a quarter-wave length, connecting at its right end with a narrow clearance space II4, having an electrical lengthalso approximately equal to a quarter-wave length, so that a low radio-frequency impedance is presented at the left-hand end of the clearance II4 as desired. The distance between the left-hand end of the choke member H3 and the flange III is made to be approximately equal to a quarter-wave length, so that the portion of transmission line extend- The segment I08 is mounted on both ends,

ing to the right of the fiange III acts as a resonant stub, and therefore, has a minimum interference with transmission of energy around the junction. Rotation of the conductor IE3 will cause the circumferential position of the segment I08 to be varied. In one position of the conductor I03 the segment I08 may be in close proximity to the segment I06. The segments I08 and I06 would then constitute a quarter-wave length transmission line open-circuited at the right-hand end, so that a relatively low radiofrequency impedance would appear across the left-hand end of such transmission line. Power may then be transmitted with relative ease from the transmission line I to the transmission line IOI. As the segment I08 is moved from such position by rotation of the conductor I03, some coupling will take place with the transmission line I02 as well as with the transmission line IOI and the power transfer to the transmission line IIlI will be reduced because the characteristic impedance of the transmission line constituted by the segments I06 and I08 will be increased. Thus anincreasing proportion of the'input power is diverted to the transmission line I02, until finally practically all of the input power is communicatedrto the transmission line I02 when the segment 108 is nearest to, the segment I31 and is shielded from the segment; I08 by the segment I09. A radio frequency power dividing circuit similar to the above-described embodiment is shown and claimedin U; S. Patent Serial No. 2,555,154, issued November 29, 1951, to R. C. Raymond and assigned to the same assignee as the present invention.

Another embodiment/of the present invention is shown in Figs. 3iand4. In Fig. 3 the input transmission line is shownat III and the output transmissionylines are shown at IIS and H9. The transmission line I'I'lpasses first through a rotating joint I20, which may be of a type described in .my abovem'entioned patent application, to connect with a transmission line I2I, which is adapted :to be rotated bodily about its axis by "means of the worm gear I22 and the worm I23. The worm 123 may be actuated by any suitable driving means.

Each of the transmission lines I2I, H8, and H9 has its respective conductors connected to a pair of quadrantal cylindrical segments. The disposition of these segments'is best seen from Fig. '4. The conductors of the transmission line I21 are connected respectively to the segments I 25 and IE; the conductors of the transmission line IIS are connected respectively to the segments I2! and I28, and conductors of the transmission line II9 are oonnected respectively to the segments I29 and I30; The segments connected to the conductors of any one of these transmission lines form an opposed pair of segments. As shown-on Fig. 4, the segments I27, 128, I29 and E33 fit together (without actual'contact, a small gap being maintained) tOZfOIm a single cylinder interrupted only by narrow :gaps. The segments I25 and I26 form an opposed pair curved to a smaller radius and oriented coaxially with the aforesaid cylinder. The segments'ove'rlap axially for a distance approximately'equal to an electrical quarter-wave length in order toiprovide efiective transfer of radio-frequency energy without actualcontact inaccordance with principles previously referred to, and are equally spaced over the entire adjacent cylindrical surfaces. Rotation 'of the transmission line I 2I is adapted to rotate the segments I25 and I26 relative to the disposition of the outer segments and thereby gradually to change the relative distribution of coupling to the two output transmission lines. When the transmission line I2I is adjusted for maximum coupling to one of the output transmission lines, there will generallybe some small power transfer to the other transmission line, but this will be very small although not exactly zero, the difference in power level being about 40 db. This degree of effectiveness is quite suiiicient for the purposes of this invention.

In order to avoid undesired couplin from stray fields that may arise in the neighborhood of the switching arrangement, quarter Wave choke cups I3I, I32 and I33 are mounted respectively on the outside of the transmission lines IEI, II 8, and H9. These prevent transmission of radio-frequency current along the outside of these transmission lines. It is further to be understood in connection with the power divider apparatus that wherever the electrical lengths of a quarter or half wave length are specified, an 'odd multiple or an even multiple, respectively, of a quarterwave length may be used equally as well. Likewise, where the ter'melectrical length, is used, it is to be understood as meaning a physical length of such value as to give the electrical effect of the corersponding electrical length in free space. Thus, the electrical lengths mentioned are to be taken as including the *contribution of end effects. All distances referred to in terms of wave lengths are intended to be electrical lengths as defined above. 7

Although I have shown and described only certain specific embodiments of the invention, I am fully aware of the many modifications possible thereof. Therefore, this invention is not to be limited except insofar as is necessitated by the prior art and the spirit of the appended claims.

I claim:

1. A radio frequency power divider, comprising a coaxial input transmission line having inner and outer conductors, a pair of coaxial output transmission lines, a cylindrical joint, said input and output lines secured to said joint, a pair of opposed curved surfaces of predetermined length used to terminate the respective conductors of said input line in said joint, two pairs of quadrantal segments, each of said quadrantal segments used to terminate the respective conductors of said output lines, said quadrantal-segments so positioned as to form a four segment cylinder circumscribing said pair of opposed curved surfaces, and means for rotating said curved segments with respect to said quadrantal surfaces.

2. A radio frequency power divider, comprising a coaxial input transmission line having inner and outer conductors, a pair of coaxial output transmission lines, a cylindrical joint, said output lines joined to said joint, a portion of said input line rotatably joined to said joint in coaxial relation with one of said output lines, a pair of opposed curved surfaces of predetermined length used to terminate the respective conductors of said input line in said joint, said opposed surfaces being positioned to provide a pair of segments of a diameter less than the outer diameter of said input line, two pair of quadrantal segments, each of said pair of segments used to terminate a respective conductor of said output lines in said joint, said quadrantal segments so positioned as to form a four segment cylinder circumscribing said pair of opposed curved surfaces, said quadrantal segments overlapp-ing'said curved surfaces byany odd multiple quarter wave length,

and a means for rotating at will said portion of said input line.

3. A radio frequency power divider, comprising a cylindrical joint, an input coaxial line, and a pair of output coaxial lines extending into said joint, a pair of spaced substantially semi-cylindrical segments connected respectively to the inner and outer conductors of a portion of said input line, and positioned concentrically with the axis of said joint, two pairs of spaced quadrantal cylindrical segments also arranged concentrically with the axis of said joint, each pair of quadrantal segments being oppositely disposed and connected respectively to an inner and outer conductor of each of the output lines, the semicylindrical and quadrantal segments being spaced axially coextensive for an odd integral number of quarter wave lengths, and means permitting rotation of said semi-cylindrical segments and associated portion of the input line, whereby the input power may be distributed between said output lines without materially disturbing the combined impedance of said output lines as seen from said input line.

4. A radio frequency power divider comprising an input coaxial line, first and second output coaxial lines, an end section of said input coaxial line being freely rotatable-about its longitudinal axis, a first pair of diametrically opposed cylindrical segments connected respectively to the inner and outer conductors of said rotatable section of said input coaxial line, said first pair of cylindrical segments being positioned concentrically with the axis of said rotatable section, two pairs of spaced quadrantal cylindrical segments also arranged concentrically with the axis of said rotatable section, the segments within each pair of quadrantal segments being diametrically opposed and connected respectively to an inner and outer conductor of a respective output coaxial line, said first pair of cylindrical segments being radially spaced from said quadrantal segments and axially coextensive with said quadrantal segments for an odd integralnumber of quarter-wave lengths.

5. A radio frequency power divider comprising an input coaxial line formed with a fixed section and a rotatable section, a rotatable joint connecting said fixed section and said rotatable section, means for controllably rotating said rotatable section, a first pair of cylindrical segments disposed at diametrically opposed points on an imaginary cylinder that is concentric with the axis of said rotatable section, said cylindrical segments being connected respectively to the inner and outer conductors of said rotatable section, two pairs of'spaced quadrantal cylindrical segments arranged around a second imaginary cylinder concentric with the axis of said rotatable section, the segments constituting each pair of quadrantal segments being diametrically opposed and connected respectively to the inner and the outer conductor of a respective output coaxial line, said first pair of cylindrical segments being radially spaced from said quadrantal segments and axially coextensive with said quadrantal segments for an odd integral number of quarter-wave lengths.

6. A radio frequency power divider comprising first and second output coaxial lines, an input coaxial line formed with a fixed section and a rotatable section; a rotatable joint connecting said fixed section and said rotatable section, means for controllably rotating said rotatable section, a first pair of cylindrical segments disposed at diametrically opposed positions about the axis of said rotatable section, said cylindrical segments being electrically connected to the inner and outer conductors, respectively, of said rotatable section and mounted so as to rotate therewith, two pairs of spaced quadrantal cylindrical segments also arranged about the axis of said rotatable section, the segments constituting each pair of quadrantal segments being disposed at diametrically opposed positions and connected respectively to the inner and the outer conductor of a corresponding output coaxial line, said first pair of cylindrical segments being radially spaced from said quadrantal segments and axially coextensive with said quadrantal segments for an odd integral number of quarter-wave lengths, and a conductive shield completely surrounding said rotatable section, said cylindrical segments, said quadrantal segments and the ends of said output lines to which said quadrantal segments are connected.

7. A radio frequency power divider as in claim 6 wherein said conductive shield includes first, second and third quarter-wave length chokes disposed on the outer conductors of said rotatable section and said two output lines respectively, said quarter-wave length chokes preventing transmission of radio-frequency current along the outside of the outer conductor.

8. A radio frequency power divider comprising a two-conductor input transmission line, first and second two-conductor output transmission lines, first and second pairs of spaced quadrantal cylindrical segments arranged about a common axis so as to form a substantially cylindrical surface, the segments constituting each pair being disposed at diametrically opposed positions and connected respectively to first and second conductors of a corresponding output transmission line, a third pair of quadrantal cylindrical segments disposed at diametrically opposed positions about said axis and connected, respectively, to a first and a second conductor of said input transmission line, said third pair of segments being radially spaced from said first and second pairs of segments and axially coextensive with said first and second pairs of segments for at least an electrical quarter-wave length, said third pair of segments being rotatable relative to said first and second pairs of segments to vary the division of power between said first and second output transmission lines.

WINFIELD W. SALISBURY.

REFERENCES CITED The following references are of record in the file of thispatent:

UNITED STATES PATENTS Number Name Date 2,445,793 Marchand July 27, 1948 

